In accordance with the recent development of the industry of parts for sintering, which have a complicated shape required in vehicles and machineries, a use amount of iron-based powder used as a raw material thereof is rapidly increased.
The parts for sintering are subjected to a process of filling the iron-based powder that is the raw material in a mold having a shape of a product manufactured to be fit for the purpose, applying a high pressure of 4 to 7 ton/cm2 to perform compressing and forming, and performing sintering treatment at high temperatures in order to provide physical and mechanical characteristics to obtain a sintered body having a high density.
Particularly, in order to manufacture sintered parts for vehicles, the powder itself should have excellent qualities such as appropriate grain size, flowability, apparent density, green density, and high cleanness so as to manufacture a high density sintered body.
It is known that since iron powder manufactured through a water atomization process does not cause a phenomenon where pores remain in a vacancy formed by reduction of oxides in the powder during a reduction process unlike reduced iron, internal pores hardly exist therein, and thus when the same pressure is applied, the iron has a green density having a high value of 0.5 g/cm3 or more as compared to the reduced iron and thus is suitable for manufacturing high density sintered parts.
Further, when the iron-based powder is manufactured, it is very important to maintain high cleanness of the iron-based powder through minimization of impurities, such as carbon (C), oxygen (O), nitrogen (N), sulfur (S), and phosphorus (P), which negatively affect compressibility.
Another important factor required in the iron-based powder together with excellent qualities such as high cleanness and high green density is economic feasibility of a manufacturing process.
In the conventional art, after scrap iron was re-melted in an arc electric furnace and subjected to a refining process including oxygen blowing such as decarburization and dephosphorization to form molten steel, iron-based powder was manufactured by a water atomization process.
However, in the conventional art, since scrap irons having different impurity contents were reused, a lot of time and costs were used to constantly maintain components of the molten steel.
Further, in general, since surface tension of the molten steel subjected to water atomization is high, there is a problem in that when the molten steel is powderized during the water atomization process, since a shape of the powder tends to become spherical, green strength of a formed material is reduced when the powder is compressed, and thus the formed material is undesirably damaged during transportation.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.
The present invention has been made in an effort to provide a method of manufacturing iron-based powder by providing an iron-based molten steel manufactured through an iron making process and a steelmaking process to a tundish, and performing water atomization over the molten steel discharged through a nozzle connected to the tundish.